The present invention relates to a device for protecting electronic components against overvoltages of the supply voltage, and in particular, but without limitation, relates to protection of electronic components used in electronic systems in motor vehicles.
It is generally known that inductive loads, such as coils and the like, produce direct or indirect overvoltages. A particularly harmful overvoltage occurs, for example, in the case of a poor contact or momentary battery disconnection during generator operation (load dump). In the automotive sector, for example, overvoltages of up to 80 V can occur within a 400 ms period in the case of a 12 V supply voltage. These transients can destroy various electronic circuits, in the motor vehicle, such as integrated circuits, unless they are effectively protected against such overvoltages.
It is possible to prevent overvoltages of the electrical system of a motor vehicle from destroying the electronic components by designing the corresponding components according to the maximum voltage peaks that occur. However, this is extremely expensive and uneconomical.
It would therefore be advantageous to provide a protective device to protect components designed for normal operation against overvoltages of the generator supply voltage.
Currently, Zener diodes are used in conjunction with the generator, that permit only slight voltage variations even when the current varies greatly.
This approach has the disadvantage that the voltage present at the Zener diode has a wide tolerance range and is greatly dependent on the temperature present at the component. During a transition to a higher vehicle system voltage (as is being planned for mass production), for example, this tolerance and temperature dependency thus becomes too great for practical application.
The device according to an embodiment of the present invention has the advantage over known approaches that it is suitable for high vehicle system voltages and is reasonably inexpensive to produce, and that the device may be positioned to prevent polarity reversal. The device also has a low tolerance and a low temperature coefficient of the response threshold.
According to an embodiment of the present invention, the device includes at least one semiconductor transistor which is switchable by a trigger circuit upon reaching predetermined overvoltage values, thereby converting electrical energy to thermal energy and protecting electronic components against system voltage overvoltages.
By switching the overvoltages of the system voltage in a defined manner via the at least one semiconductor transistor, the load dump energy is converted to heat by the semiconductor component and the internal resistor of the supply voltage source, thus protecting the connected electronic components against damage by the original load dump energy.
According to an embodiment, the trigger circuit and the semiconductor transistor are provided as integrated circuits on a single chip.
According to another embodiment, the semiconductor transistor is electrically connectable in series to a Zener diode. The Zener diode stabilizes the voltage and coverts electrical overvoltage energy to thermal energy.
According to another embodiment, the semiconductor transistor and the Zener diode are provided as integrated circuits on two separate chips. In this case, the two chips may be either stacked or arranged side-by-side and then electrically interconnected.
According to another embodiment, the device is at least partially surrounded by at least one heat removal apparatus. This makes it possible to remove the heat generated in the semiconductor components from the components and to discharge it to the environment.
According to a further embodiment, at least one heat removal apparatus is designed as a metal body, a casting compound, for example an epoxy compound, and/or a metal receptacle. The one or more heat removal apparatuses may be placed into direct contact with the corresponding semiconductor components.
According to a further embodiment, the semiconductor transistor is designed as a MOSFET transistor, for example, a vertical power MOSFET transistor, having an integrated trigger circuit.
According to a further embodiment, the semiconductor transistor is designed as a vertical bipolar transistor having an integrated trigger circuit.
According to a further embodiment, the electrical connections of the device are designed as soldered connections and/or direct die bonding connections.
According to a further embodiment, the Zener diode is connected in series to a rectifier diode. This makes it possible to prevent the component from being damaged in the event of a polarity reversal, for example by using an n+-p-n semiconductor component.
According to a further embodiment, the Zener diode and the rectifier diode are integrated into a three-layer semiconductor element.
According to a further embodiment, the device may be provided in an electronic system of a motor vehicle to protect the system components against overvoltages of the motor vehicle electrical system.